Conventionally, the production of a printing plate from a PS plate (presensitized printing plate) includes a wet developing process for imagewise removing a photosensitive layer formed on the surface of a support after light exposure and a post-treatment process of washing a developed printing plate with washing water and treating the printing plate with a rinse solution containing a surface active agent and with a desensitizing solution containing gum arabic and a starch derivative.
Recently, in the plate-making and printing industries, the rationalization of the plate making work has been promoted, and an original for a printing plate, which can be used for printing as it is after exposure without need of the complicated wet development process as described above and further does not generate alkaline developer waste solution in the developing, has been desired.
An original for a printing plate that does not require a developing process after imagewise exposure, for example, a planographic printing plate formed by laminating on a support a photosensitive hydrophilic layer, the curing and insolubilization of which are accelerated in the light-exposed region together with a photosensitive hydrophobic layer, is disclosed in U.S. Pat. No. 5,258,263. However, because the printing plate has a two-layer structure, adhesion between the upper layer and the lower layer becomes a problem, and a large number of prints cannot be printed.
Also, as a planographic printing original that does not require a wet development process after image forming, a printing material provided with a silicone layer and a laser-thermosensitive layer under the silicone layer is disclosed in U.S. Pat. Nos. 5,353,705 and 5,379,698. Although these printing materials do not require a wet development process, they have the drawback that treatment by rubbing or with a specific roller is required to complete the removal of the silicone layer with laser abrasion, which makes the process complicated.
Also, it is disclosed in Japanese Patent Laid-Open (JP-A) Nos. 5-77574, 4-125189. Japanese Patent Application Publication (JP-B) No. 62-195646, and U.S. Pat. No. 5,187,047 that by using a film obtained by sulfonating a polyolefin and changing the hydrophilic property of the surface thereof by thermal writing, a printing material without need of a development process is formed. In the system, images are formed by desulfonating the sulfone groups on the surface of the printing material and the development process becomes unnecessary, but the system has drawback that a noxious gas is generated during the thermal writing.
Furthermore, U.S. Pat. Nos. 5,102,771 and 5,225,316 disclose a printing material prepared by combining a polymer having an acid-susceptible group in the side chain and a photo acid generating agent, and propose a system which dispenses with a developing process. However, the printing material has the drawback in that because the acid generated by the printing material is a carboxylic acid, the extent of the hydrophilic property is decreased and the printing material is liable to be stained, whereby the printing material is inferior in the durability of the printing material and the sharpness of the printed images.
Also, JP-A No. 4-121748 discloses a printing material prepared by combining a polymer having a sulfonic acid ester group in a side chain, an acid generating agent, and a dye, but in the system, the printing material is developed using an alkaline developing solution and there are no proposals for any system which employs water-processing or dispenses with a developing process.
As radiation-sensitive image-forming material suitable for the production of a printing material for positive type processing-free planographic printing, the image-forming material is known as described in JP-A No. 7-186562 and also is described in JP-A Nos. 9-26878 and 9-26877 by the present inventors. In the patent publication and patent specifications are described compounds each composed of a specific carboxylic acid ester or a sulfonic acid ester structure and having a functional group capable of changing from a hydrophobic property to a hydrophilic property by heating or by the action of an acid and a functional group capable of reacting with a hydrolytic polymerizable compound having a trimethoxysilyl group. By using these compounds, printing materials which can perform printing without performing a development process after exposure, and satisfactory prints can be obtained, but further improvement in printing durability is still desired.